I. Field of the Invention
The present invention relates to a method of and apparatus for detecting and signifying the presence or absence of a mark on a transparent substrate or sheet.
II. Technological Environment of the Invention
A presently available method known by the applicant for detecting and signifying the presence or absence of a product identity mark or the like, e.g., a trademark, design mark, symbol, etc., on a sheet, is to view the sheet, with the unaided eye, to determine presence or absence of the mark. This manual visual inspection becomes more difficult and expensive within the context of a production line of a glass manufacturing plant, because of fatigue and human error. It is therefore desirable and advantageous to provide a method and apparatus for automatically detecting the absence or presence of a product identity mark or the like on a transparent sheet, and to automatically signal the absence of the mark.